6101 23RD DR W NORPRO Geotech Report 2025-07-29

I June 3,2011 Project No.T-6578 I 4.3 Seismic Hazard Area IPer section 37.080(2)(a & b) of the EMC, seismic hazard areas are as determined by the referenced Dames and Moore publication and the Snohomish County Liquefaction Susceptibility Map. Based on Section 3.3.3 of the referenced Dames and Moore publication, "seismic hazard exists under anyone of the following conditions or I combinations thereof: a. Areas underlain by potentially cohesionless soils of low density in associates with shallow groundwater, which may include river drainages,beach areas, ponds,and lakes. b. Areas mapped by Dames and Moore as having liquefaction potential and high site amplification." ILiquefaction is a phenomenon where there is a reduction or complete loss of soil strength due to an increase in water pressure induced by vibrations. Liquefaction mainly affects geologically recent deposits of fine-grained Isands underlying the groundwater table. Soils of this nature derive their strength from intergranular friction. The generated water pressure or pore pressure essentially separates the soil grains and eliminates this intergranular Ifriction; thus,eliminating the soil's strength. Based on the dense to very dense, cohesive nature of the native site soils and the lack of an established groundwater table in our explorations, it is tour opinion that the risk for liquefaction to occur at this site during an earthquake is negligible. 1 The City of Everett Liquefaction (Seismic) Hazard Critical Areas Map 4 indicates the site is not located in an area with the potential for liquefaction. The Snohomish County Liquefaction Susceptibility Map indicates that Ithe site is located in an area of very low to low liquefaction potential. Based on the soil and groundwater conditions at the site, in addition to review of the municipal maps, it is our opinion that the site would not be classified as a seismic or liquefaction hazard area as defined by the EMC. 4.2 IBC Seismic Parameters IBased on the soil conditions encountered and the local geology, the 2009 International Building Code (IBC) indicates that site class "C" should be used in structural design. For this site class and project location, the Ifollowing seismic parameters should be used in structural design: ISeismic Design Parameters(IBC 2009) Spectral response acceleration(Short Period), SS 1.250 1 Spectral response acceleration (1-Second Period), Si 0.446 Site coefficient at Short Periods,Fa 1.000 Site coefficient at 1-Second Periods, F, 1.354 1 Five percent damped 0.2-second period, Sns 0.834 Five percent damped 1-second period, SDI 0.402 IValues based on Latitude 47.9428N and Longitude -122.2628W, taken from Ground Motion Parameter Calculator accessed May 27,2011 on the web site http://earthq take.uses.i ovfresearchlhazmapsidesigniindex.php I Page No.5